1. Field of the Invention
The present invention relates to a water and gas cooling system for cooling a shaft and fan blade of a blower assembly in a high temperature heat treatment environment.
2. Description of the Related Art Including Information Disclosed Under 37 CFR .sctn..sctn. 1.97-1.99
In heat treatment apparatus, an anti-oxidizing filler gas or atmosphere containing hydrogen, carbon monoxide and nitrogen is used to suspend methane for carburization, is referred to as an endothermic gas and is supplied to a non-oxidizing heat treatment oven chamber.
Endothermic gas is referred to as Rx gas and is used in heat-treating. The ratio of the components of Rx may vary slightly depending on the fuel gas from which the Rx gas is derived but its function in a heat-treatment process is constant. Rx gas provides a suspension medium for other process gases such as methane and ammonia. Although Rx gas is not really "inert" it is used like an inert gas in many industrial applications.
The anti-oxidizing filler gas or atmosphere is supplied to a heat treatment chamber and circulated therein by a fan or blower. In such devices, a shaft extends through a water cooling jacket to a fan blade inside the heat treating chamber where the shaft is fixed to the fan blade. The other end of the shaft is coupled to a motor shaft. Since high temperatures of up to 2,000.degree. F. are encountered inside the heat treatment chamber, the life of the fan blade and shaft is limited and typically have to be replaced every six months and definitely by one year of use.
Heretofore, the anti-oxidizing filler gas has typically been injected into the heat treatment chamber from a side wall thereof adjacent or near the fan blade of the blower or fan.
Examples of heat treatment apparatus are disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 4,236,941 Main, Jr. 4,272,239 Thekdi et al. 4,743,197 Bloom 4,769,090 Queille 4,867,808 Heilmann et al. 4,909,732 Wingens 5,052,921 Hemsath 5,064,173 Ecalle et al. 5,539,853 Jamaluddin et al. 5,478,057 Wilhelmi et al. 5,591,274 Takahashi 5,611,685 Nakajima et al. ______________________________________
The Bloom U.S. Pat. No. 4,743,197 discloses a high temperature fan plug for a jet heat recuperator which includes inner and outer face plates spaced apart by tubular spacers extending between the plates to form a heat insulative cavity.
The Wingens U.S. Pat. No. 4,909,732 discloses a heat treatment furnace having a housing surrounding a heating chamber having cooling gas inlets and outlets connected to a cooling gas circulation system for circulating the gas.
The Jamaluddin et al. U.S. Pat. No. 5,539,853 discloses a down hole heating system with separate wiring cooling and heating chambers with gas flow therethrough.
In view of the high temperatures encountered in heat treatment of parts, the fan blade and shaft need to be replaced frequently, typically every six months.
As will be described in greater detail hereinafter, the present invention provides a water and gas cooling system for the shaft and fan blade of a blower assembly for use in a heat treatment chamber that minimizes erosion of the shaft and fan blade or impeller and extends the useful life of the shaft and fan blade by a significant factor, e.g., up to ten. Stated otherwise, the method and apparatus of the present invention can increase the life of the shaft and fan blade from six months to over two years.
By directing the "inert" gas along the shaft into the impeller, erosion is minimized if not altogether eliminated. Typically, on fans where the impeller is relatively close to a protective jacket, i.e., within three inches, gas and debris become trapped in a "dead" area around the shaft just above the impeller. This results in severe erosion problems and premature failure of the alloy(s) from which the shaft and impeller are made. Directing the "inert" process gas along the shaft directly into the impeller eliminates this "dead" area and the consequential erosion problems. Further, due to the dynamic action of the shaft and impeller, the atmosphere inlet becomes self cleaning.
The increase in life of the shaft and fan blade is brought about by directing the anti-oxidizing filler gas radially inwardly to a cylindrical enclosure surrounding the shaft just below a water cooling jacket with a gas inlet pipe and by directing the anti-oxidizing filler gas with the cylindrical enclosure downwardly along the shaft within an insulative housing and to the fan blade.